ARM North Slope Alaska, Cloud Measurements
Entry ID:
NSAcloud
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Summary
Abstract:
The Atmospheric Radiation Measurement (ARM) Program is the largest global change research program supported by the U.S. Department of Energy (DOE). ARM scientists focus on obtaining field measurements and developing models to better understand the processes that control solar and thermal infrared radiative transfer in the atmosphere (especially in clouds) and at the earth's ... surface.
The URL for the ARM Data Archive is http://www.archive.arm.gov/. The URL for
general information about the ARM program is http://www.arm.gov/.
The data stored by the ARM Archive includes numerous parameters about radiative
flux, meteorology, water vapor and clouds.
The North Slope of Alaska/Adjacent Arctic Ocean (NSA/AAO) site is providing
data about cloud and radiative processes at high latitudes. These data are
being used to refine models and parameterizations as they relate to the Arctic.
The NSA/AAO site is centered at Barrow and extends to the south (to the
vicinity of Atqasuk), west (to the vicinity of Wainwright), and east (to
Oliktok).
Cloud measurements at Barrow and Atqasuk use many specialized instruments.
Detailed information on each instrument is available at
http://www.arm.gov/docs/instruments.html.
The following list contains the instrumentation used to monitor clouds and the
data available for the Barrow (C1) and Atqasuk (C2) sites.
Vaisala Ceilometer (VCEIL). For complete VCEIL information, visit
http://www.arm.gov/instruments. The VCEIL is a
self-contained, ground-based, active, remote-sensing device designed to measure
cloud-base height at up to three levels and potential backscatter signals by
aerosols. Model CT25K has a maximum vertical range of 25,000 feet. The
ceilometer transmits near-infrared pulses of light, and the receiver telescope
detects the light scattered back by clouds and precipitation. The Vaisala
ceilometers measure the backscattered light intensity from a pulsed InGaAs
diode laser (905 nm) as a function of distance (15-m resolution for the CT25K).
These measurements are used to produce derived products that are recorded.
These products include (1) The backscatter profile with 15-m resolution; (2)
The cloud-bottom height determined with an algorithm to define cloud bottom as
the height corresponding to a visibility reduction to 100 m; (3) Secondary
cloud-bottom heights from a cloud above the lowest cloud; and (4) Tertiary
cloud-bottom heights from an even higher cloud.
VCEIL data at Barrow are available for 1997-12-11 to present.
At Atqusck, the data are available for 1999-08-22 to present.
ARM data stream is coded as follows:
nsavceil25k: cloud base heights, 25,000 feet maximum range.
Additional data streams or value added products may be added in the future.
Millimeter Wave Cloud Radar (MMCR).
For complete MMCR information, visit
http://www.arm.gov/instruments. The MMCR systems probe
the extent and composition of clouds at millimeter wavelengths. The MMCR is a
zenith-pointing radar that operates at a frequency of 35 GHz. The main purpose
of this radar is to determine cloud boundaries (e.g., cloud bottoms and tops).
This radar will also report radar reflectivity (dBZ) of the atmosphere up to 20
km. The radar possesses a doppler capability that will allow the measurement of
cloud constituent vertical velocities. The primary quantities measured with
this system are (1) radar doppler spectra, (2) radar doppler moments, (3) radar
reflectivity (dBZ), (4) vertical velocity, and (5) spectral width. Inversions
are in development to infer cloud microphysical properties.
At Barrow (C1), MWR data are available from 1998-01-02 to present.
ARM data streams are coded as follows:
nsammcrmomentsC1: moments data
nsammcrmonC1: moments data
nsammcrpowC1: power data
nsammcrcalC1: calibration data
nsammcrmode01v0091clothC1: Drived: MMCR Mode 1 (stratus mode) moments
nsammcrmode02v0061clothC1: Derived: MMCR Mode 2 (cirrus mode) moments
nsammcrmode03v0081clothC1: Derived: MMCR Mode 3 (general mode) moments
nsammcrmode04v0061clothC1: Derived: MMCR Mode 4 (robust mode) moments
Additional data streams or value added products may be added in the future.
The Micropulse Lidar (MPL). For complete MPL information, visit
http://www.arm.gov/instruments. The MPL is a ground-based
optical remote sensing system designed primarily to determine the altitude of
clouds overhead and provides information on cloud base (thick clouds), cloud
base and top (optically thin clouds) and an aerosol profile. The physical
principle is the same as for radar. A pulse of energy is transmitted and the
energy reflected back is measured. From the time delay between the transmitted
pulse and the backscattered signal, the distance to the scatterer is inferred.
Besides real-time detection of clouds, post-processing can also characterize
the extent of the tropospheric mixing layer (the planetary boundary layer), or
other particle-laden regions. This eye-safe system is designed for continuous
operation. The Micropulse Lidar (MPL) has one measurement channel that records
backscatter signals in 300 meter range bins, with the lowest valid range bin
beginning at 120 meters above ground level, up to 20+ kilometers. The primary
quantity obtained from this signal is the real-time reporting of the lowest
detected cloud base in meters, obtained from 60 sec averages. Additional
quantities possible through post-processing of the raw signal return include a
relative backscatter profile (counts/sec/meter) with instrument effects
removed. Instrument effects include a dead-time correction specific to the
individual detector, near-range corrections for the overlap of the transmitting
and detection optics, and removal of afterpulsing due to detector saturation
from optical crosstalk as the pulse is transmitted. From the relative
backscatter profile, other data products are possible. These include cloud
boundaries, multiple cloud decks, and layer boundaries.
At Barrow (C1), MPL data are available from 1998-05-21 to present.
ARM data streams are coded as follows:
nsamplC1: cloud base and top heights
nsamplcmask1clothC1: MPL cloud mask using the first Clothiaux, et al. Algorithm
nsamplsmask1clothC1: MPL significance mask using the first Clothiaux, et al.
Significance Algorithm.
Additional data streams or value added products may be added in the future.
Microwave Radiometer (MWR).
For complete MWR information, see
http://www.arm.gov/instruments. The MWR provides
time-series measurements of column-integrated amounts of water vapor and liquid
water. The instrument itself is essentially a sensitive microwave receiver.
That is, it is tuned to measure the microwave emissions of the vapor and liquid
water molecules in the atmosphere at specific frequencies. The MWR receives
microwave radiation from the sky at 23.8 GHz and 31.4 GHz. These two
frequencies allow simultaneous determination of water vapor and liquid water
burdens along a selected path. Atmospheric water vapor observations are made at
the hinge point of the emission line where the vapor emission does not change
with altitude (pressure). Cloud liquid in the atmosphere emits in a continuum
that increases with frequency, dominating the 31.4 GHz observation, whereas
water vapor dominates the 23.8-GHz channel. The water vapor and liquid water
signals can, therefore, be separated by observing at these two frequencies.
At Barrow (C1), MWR data are available for 1998-01-02 to present.
At Atqusk (C2), MRW data are available for 1999-10-18 to present.
ARM data streams are coded as follows:
nsamwrlos: water liquid and vapor along line of sight path
nsamwrtip: airmasses, brightness temperatures in TIP mode
nsa5mwravg: 5-minute average integrated vapor and liquid water
nsaqmemwrcol: Derived: QME comparing column water from MWR vs. instrument model
Additional data streams or value added products may be added in the future.
Whole-Sky Imager (WSI).
For complete information on the WSI, see
http://www.arm.gov/instruments. The WSI is an automated
imager used for assessing and documenting cloud fields and cloud field
dynamics. The WSI is a ground-based electronic imaging system that monitors the
upper hemisphere. It is a passive, i.e., non-emissive, system that acquires
images of the sky dome through three spectral filters (neutral, red, and blue).
From these sky images, we can assess the presence, distribution, shape, and
radiance of clouds over the entire sky using automated cloud decision
algorithms and related processing. The present WSI model (EO System 6) is
capable of image acquisition under daylight, moonlight, and starlight
conditions. The WSI measures the sky radiance in approximately 1/3 degree
increments over the entire sky dome. The measurements are made in two narrow
spectral regions centered at 650 nm and 450 nm. The sky radiances are acquired
as two 16-bit images and are used to determine the presence of opaque clouds
and thin clouds in the line of sight on a pixel-by-pixel basis. These cloud
data are used to calculate the cloud cover and statistical quantities.
At Barrow (C1), WSI data are available for 1998-10-19 to present.
At Atqusk (C2), WSI data are available for 2001-09-14 to present.
ARM data streams are coded as follows:
nsawsicloud: Derived: cloud numbers, area, perimeter, and more from the WSI
nsawsicloudsummary: cloud and aerosol information, classification summary data
nsawsifullradiance: calibrated radiances for each pixel, with multiple filters
nsawsipatchsummary: radiances from red image for three patches (average and
standard deviation).
Additional data streams or value added products may be added in the future.
Active Remote Sensing Cloud Layer (ARSCL).
For Barrow (C1) there are two additional data streams that use data from the
Belfort laser ceilometer (BLC), MPL, and MMCR. The BLC was replaced by the
VCEIL in 2000. For information on the BCL, see
http://www.arm.gov/instruments.
ARSCL data are available for 1998-11-01 to present.
ARM data streams are coded as follows:
nsaarsclbnd1cloth: cloud boundaries from first Clothiaux algorithms on BLC,
MPL, MMCR
nsaarsclcbh1cloth: cloud base height from first Clothiaux algorithms on BLC,
MPL, MMCR
Additional data streams or value added products may be added in the future. 
Related URL
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Description:
NCVweb is an interactive web-based tool for viewing atmospheric radiation
measurement (ARM) data.
Description:
This catalog lists the data streams that are currently available from the ARM
Archive. The data streams are listed by file format type (i.e, CDF, HDF, RAW,
JPG, ASC, and Other) and then by the site where the data are collected. Each
list contains the name of the data streams in alphanumeric order, the number of
files within the data stream, the minimum data date, and the maximum data date.
The sites that have the word development in parenthesis are data processes
which are operated during the final phases of implementation of a data source,
resulting in data which are labeled as Development. Development data are
frequently available to users, but additional information about the operating
conditions and potential for errors must be considered. The files in CDF format
are also listed in preformatted lists for those browsers that have difficulty
handling large html tables. The information in this catalog is updated about
once a month.
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Geographic Coverage
(Click for Interactive Map)
Spatial coordinates
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N: 71.32
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S: 70.47
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E: -156.62
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W: -157.41
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Data Set Citation
Dataset Originator/Creator:
Wanda Ferrell, Ted Cress, Thomas Ackerman
Dataset Title:
ARM North Slope Alaska, Cloud Measurements
Data Presentation Form:
netCDF files
Online Resource:
http://www.arm.gov
Quality
The data is described in the publications. All existing samples are held by Landcare Research in their Ross Sea Region Soils Database.
Data Set Progress
COMPLETE
Personnel
Role:
INVESTIGATOR
Phone:
64 3 547 3329
Fax:
64 3 547 3329
Email:
iaincampbell at xtra.co.nz
Contact Address:
Land and Soil Consultancy Services
23 View Mount
City:
Nelson
Country:
New Zealand
Role:
INVESTIGATOR
Email:
graeme.claridge at xtra.co.nz
Contact Address:
Land and Soil Consultancy Services
23 View Mount
City:
Nelson
Postal Code:
7001
Country:
New Zealand
Role:
DIF AUTHOR
Phone:
+64 3 358 0200
Fax:
+64 3 358 0211
Email:
c.poirot at antarcticanz.govt.nz
Contact Address:
Antarctica New Zealand
Private Bag 4745
City:
Christchurch
Country:
New Zealand
Role:
DIF AUTHOR
Phone:
+64 3 358 0200
Fax:
+64 3 358 0211
Email:
s.gordon at antarcticanz.govt.nz
Contact Address:
Antarctica New Zealand
Private Bag 4745
City:
Christchurch
Country:
New Zealand
Publications/References
Campbell, I. Balks, M. The state of the Ross Sea region terrestrial environment: Soils and ice-free areas. In: Ross Sea Region 2001: A state of the environment report for the Ross Sea region of Antarctica.Waterhouse E.(ed) Christchurch: New Zealand Antarctic Institute. 2001. pp.4.16-4.33 ISBN 047810961X
Campbell, I.B. Claridge, G.G.C. Permafrost properties, patterns and processes in the Transantarctic Mountain region. Permafrost and periglacial processes 17: 215-232 doi:10.1002/ppp.557, 2006.
Campbell, I.B. Claridge, G.G.C. Balks, M.R. 1994 The effect of human activities on moisture content of soils and underlying permafrost from the McMurdo Sound region, Antarctica. Antarctic science 6(3): 307-314
Campbell, I.B. Claridge, G.G.C. Balks, M.R. 1992 The properties and genesis of cryosols at Marble Point, McMurdo Sound region, Antarctica. Cryosols: the effects of cryogenesis on the processes and peculiarities of soil formation; proceedings of the First International Conference on Cryopedology, Nov. 1992, Pushchino. Gilichinskii, D.A. (ed), Pushchino Russian Academy of Sciences
Campbell, I.C., Claridge, G.G.C., Campbell, D.I. And Balks, M.R. 1998. Soil temperature and moisture properties of cryosols of the Antarctic Cold Desert. Eurasian Soil Science 31: 542-546.
Creation and Review Dates
DIF Creation Date:
2008-11-04
Last DIF Revision Date:
2009-03-25
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